The advent of the sewing machine changed the face of the garment industry from tiny, store-front shops with a few seamstresses and tailors, into a multi-billion dollar per year operation. The sewing machine provided a fast and effective way to stitch fabric while maintaining or even surpassing the high degree of quality found in hand stitched garments. Moreover, large numbers of a single type of garment could be produced in a greatly reduced amount of time. However, sewing machines were limited by the fact that certain garments required the looping and stitching of an additional thread to properly join two pieces of fabric. This additional thread was supplied by a secondary thread source or bobbin. Bobbins were extremely limited in their thread capacity and frequently required changing. Once a bobbin was emptied of its thread, a sewing machine operator would have to stop the stitching process, manually remove the empty bobbin, replace it with a full bobbin, rethread the needle hook and needle and resume stitching. This became a time consuming process and sometimes led to poor garment construction or damaged the delicate fabrics being joined. Since the success of a garment manufacturer depended mostly on the ability to constantly supply quality clothing in a timely manner, there arose a need for a bobbin mechanism that had an increased thread supply or was capable of continuous bobbin replacement feeding to reduce "down time" during sewing machine operation.
Various improvements in bobbin technology have been made. Rovin et al. (U.S. Pat. No. 4,002,130) teaches an automatic bobbin rewinding mechanism whereby an empty bobbin and its case are removed from a sewing position and inserted to a rewinding position, while simultaneously, a filled bobbin is removed from the rewinding position and inserted to a sewing position. However, the procedure of transferring the bobbins from rewinding to sewing positions requires various mechanical components including actuators, cams, gear drives, etc. which results in a bulky frame needing to be bolted to the existing sewing machine.
Mardix et al. (U.S. Pat. No. 5,143,004) teaches a sewing apparatus which comprises a sewing needle, a bobbin for feeding thread to the sewing needle, a rotary housing containing the bobbin and its case, a sensor for sensing the non-feeding of thread to the sewing needle and an automatic extraction-loading device for extracting an empty bobbin and replacing it with a full one. This automatic bobbin-reloading system also utilizes a series of rotary actuators, pistons, etc. to remove and refill bobbins. Also, an optical sensor to detect bobbin thread-breakage or -exhaustion further adds to the complexity of the device.
Kosmas (U.S. Pat. No. 4,681,050) teaches a bobbin run-out detector and bobbin changing mechanism. The mechanism comprises a carriage which supports a rotatable turret that holds a pair of bobbins. The run-out detector, similar to that of Mardix, is also an optical sensor device. This machine however is limited in that upon detection of an empty bobbin, it must stop the sewing operation to rotate the turret to move the full bobbin into the sewing position, retract the empty bobbin and replace it with the full bobbin. Further, once the full bobbin is in position, an additional step to resynchronize the hook and bobbin is employed before sewing can continue.